Sintesi di polimeri funzionali contenenti complessi poliossometallati per ossidazioni catalitiche eterogenee.

In this Thesis new hybrid materials, based on polymeric methacrylates and polyoxometalates (POMs) , have been prepared by means of radical polymerization. Vacant-type Keggin POMs have been functionalised with 2-4 unsaturated alkyl chains (1-ottenyl) and used as monomers together with methylmetacrylate (MMA). Different proportions of a cross-linker, ethylenglycoldimethacrylate (EDM), have also been added to tune the properties of the resulting material. Porogenic solvents (1,4 butanediol and 2-propanol have been successfully used to obtain porous polymers with swelling capabilities in polar solvents (up to 4g/g in acetonitrile). Catalytic tests have been carried out on a model reaction: the oxidation of methyl p-tolyl sulfide, in acetonitrile, in the presence of hydrogen peroxide. This study has allowed to identify (i) the most reactive polioxoanions; (ii) an optimal composition for the synthesis of the polymers; (iii) reaction conditions useful to increase the efficiency of the catalytic process. The complex [(CH3CH2CH2CH2)4N]3H[(CH2=CH(CH2)6Si)2O(SiW10O36)] shows a good reactivity at 50°C (complete H2O2 conversion in 130 min, with average TOF of 17 h-1), and it seems to be the most suitable for the preparation of polymers (with composition [POM]/[MMA]/[EDM] 40:30:30 w/w) with reproducible morphology (pore diameter of 200 nm) and homogeneous POM distribution. The catalytic system is suitable for the development of a sustainable process because (i) the oxidation is carried out with a green oxidant, (ii) in mild conditions, and (iii) it can be recovered upon filtration when used as monolithic polymer. Indeed, the catalytic system has been used for the oxidation of dibenzothiophene in octane, as a model for the organic sulfides in fuels, with H2O2. Preliminary data shows a complete conversion of dibenzothiophene to the correspondent sulfone in about 4h (TOFmax= 18 h-1).